Polypropylene-based resin composition and molded article

ABSTRACT

Disclosed are: a polypropylene-based resin composition comprising 100 parts by mass of polypropylene-based resin (A) (provided that, when the polypropylene-based resin includes other resins and/or inorganic filler, the total amount of the polypropylene-based resin and other resins and/or inorganic filler is taken as 100 parts by mass), 0.80 to 5.0 parts by mass of on or more types of aluminum flakes (B) having an average particle size of 5 to 90 μm, and 0.005 to 0.06 parts by mass of carbon black (C); and a molded article obtained by injection-molding this polypropylene-based resin composition. The polypropylene-based resin composition and the molded article obtained from this are excellent in a flip-flop metallic feeling, a heavy luxury feeling, light resistance and a feeling of luminance.

RELATED APPLICATIONS

The present application claims priority under 37 U.S.C. § 371 toInternational Patent Application No. PCT/JP2018/006368, filed Feb. 22,2018, which claims priority to and the benefit of Japanese PatentApplication No. 2017-035679, filed on Feb. 28, 2017. The contents ofthese applications are hereby incorporated by reference in theirentireties.

TECHNICAL FIELD

The present invention relates to a polypropylene-based resin compositionexcellent in a flip-flop metallic feeling, a heavy luxury feeling, lightresistance and a feeling of luminance, and a molded article obtainedfrom this polypropylene-based resin composition.

BACKGROUND ART

Because of merits of plastics such as light weight, cheapness and easymolding, metal materials, inorganic materials and wood materials havebeen replaced with plastics in molded articles, contributing greatly tolife of people, economy and environment. However, the appearance andfeel of plastic molded articles may be given a cheap impression comparedto molded articles made of metallic materials, inorganic materials orwood. Therefore, it is very significant to provide a plastic moldedarticle which feels like a metal or has a heavy luxury feeling.

On the other hand, Patent Document 1 discloses a metallic paintcontaining an aluminum foil (aluminum flake). A molded article coatedwith a metallic paint has a flip-flop property that a color tone(lightness) felt visually is different depending on a viewing angle,that is, a difference in light receiving angle of emitted light of lightreflected on a painted surface.

In recent years, in the field of automotive exterior materials,techniques for obtaining a resin molded article having a metallicfeeling equivalent to that of a coated article have been studied. Forexample, Patent Document 2 describes that a thermoplastic resincomposition having a flip-flop metallic feeling can be obtained by usingaluminum flakes having a small particle size and pearl mica together.Here, the larger the difference in lightness between the highlightdirection (the regular reflection direction with respect to the incidentangle of light) and the shade direction (the non-regular reflectiondirection), the more human feels a metallic feeling, so it is requiredthat this flip-flop property is high.

Patent Document 3 describes that, by using two or more kinds of aluminumflakes differing in average particle size as the brightener, it ispossible to impart a high flip-flop property and a brilliance close topainting to an injection molded article. Patent Document 4 discloses acomposition composed of a thermoplastic resin, a fibrous inorganicfiller, a brightener (aluminum flake) and a colorant. As the colorant,0.3 parts by mass of carbon black is blended. However, when 0.3 parts bymass of carbon black is added as the colorant, the lightness is lowregardless of the angle of light reception, so that a flip-flop metallicfeeling does not appear.

Patent Document 5 discloses a resin molded article containing a basematerial made of a thermoplastic resin, a black colorant (carbon black),and a particulate brightener (aluminum particles). It is described thata metallic tone appearance can be obtained as if many brighteners arecontained even if the content of the brightener is small. However, thecontent of the brightener specifically used in the examples is 0.6% bymass, and such a small amount does not sufficiently exhibit a feeling ofluminance.

Patent Document 6 discloses a metallic-like engine cover made of a resincomposition containing polymethylpentene, polypropylene, a fibrousfiller, a colorant and a brightener (aluminum particle). However, thisresin composition is insufficient in terms of a flip-flop metallicfeeling and a luxury feeling, and is not suitable as a material of apart where the appearance is very important.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: JP S62-106870

Patent Document 2: JP 2006-009034

Patent Document 3: JP 2014-076626

Patent Document 4: JP 2009-035713

Patent Document 5: JP 2000-309638

Patent Document 6: JP 2013-227488

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a polypropylene-basedresin composition excellent in a flip flop metallic feeling, a heavyluxury feeling, light resistance and a feeling of luminance, and amolded article obtained from the polypropylene-based resin composition.

Solution to Problem

The present inventors have intensively studied to attain theabove-described object and resultantly found that when aluminum flakesand carbon black are added each in specific amounts to apolypropylene-based resin composition excellent in light resistance, thesynergetic effects of both are manifested remarkably and high-grademetallic feelings including a flip flop metallic feeling, a heavy luxuryfeeling and a feeling of luminance are obtained, leading to completionof the present invention.

Furthermore, the inventors of the present invention have found that whenthe ratio of lightness in the highlight direction (regular reflectiondirection with respect to incident angle of light) and lightness in theshade direction (non-regular reflection direction) of a molded articleobtained from such a resin composition is a certain value or more andwhen the lightness in the shade direction is a certain value or less,high-grade metallic feelings including a flip-flop metallic feeling, aheavy luxury feeling and a feeling of luminance can be obtained, leadingto completion of the present invention. That is, the present inventionis specified by the following matters.

[1] A polypropylene-based resin composition comprising

100 parts by mass of a polypropylene-based resin (A) (provided that,when the polypropylene-based resin contains other resins and/orinorganic fillers, the total amount of the polypropylene-based resin andthe other resins and/or inorganic fillers is taken as 100 parts bymass),

0.80 to 5.0 parts by mass of one or more kinds of aluminum flakes (B)having an average particle size of 5 to 90 μm and

0.005 to 0.06 parts by mass of carbon black (C).

[2] The polypropylene-based resin composition according to [1], wherein

when incident light is irradiated from the direction of 45° to thesurface of a test piece obtained by molding the polypropylene-basedresin composition by the following injection molding method, thelightness in the highlight direction (L15°) and the lightness in theshade direction (L110°) defined below satisfy the followingrelationship:L15°/L110°≥3.3L110°≤27.0[Lightness in Highlight Direction (L15°)]

When the regular reflection position of 90° with respect to the incidentlight at 45° is defined as 0°, the lightness in the highlight direction(L15°) is the lightness of the reflected light at an angle shiftedtoward the incident light direction side by 15° from this 0°.

[Lightness in Shade Direction (L110°)]

When the regular reflection position of 90° with respect to the incidentlight at 45° is defined as 0°, the lightness in the shade direction(L110°) is the lightness of the reflected light at an angle shiftedtoward the incident light direction side by 110° from this 0°.

[Injection Molding Method]

The polypropylene-based resin composition is injection-molded underconditions in which the barrel temperature is higher by (20 to 120°) C.than the highest temperature of the glass transition temperature and/orcrystal melting temperature of the resin, the injection speed is 30 to50 mm/sec, the mold set temperature is lower by (50 to 100°) C. than thehighest temperature of the glass transition temperature and/orcrystallization temperature of the resin, the cooling time is 10 to 20seconds, and the mold clamping pressure is 30 to 80 t, to obtain a testpiece composed of a square plate with a thickness of 2 mm.

[3] The polypropylene-based resin composition according to [1], furthercomprising 0.01 to 0.70 parts by mass of a chromatic inorganic pigmentand/or organic pigment (D) (excluding carbon black).

[4] The polypropylene-based resin composition according to [1],comprising 70 to 100 parts by mass of a polypropylene-based resin(provided that, when the polypropylene-based resin contains otherresins, the total amount of the polypropylene-based resin and the otherresins is 70 to 100 parts by mass) and 0 to 30 parts by mass of aninorganic filler.

[5] A molded article obtained by injection-molding thepolypropylene-based resin composition according to [1].

[6] The molded article according to [5], which is an automotive exteriormaterial.

Advantageous Effect of Invention

In the polypropylene-based resin composition of the present invention,by adding specific aluminum flakes and carbon black in appropriateamounts respectively, surprisingly, a flip-flop metallic feeling and afeeling of luminance improve remarkably, a heavy luxury feeling ismanifested by the decrease in lightness only in the horizontal directionwith respect to the surface of the molded article, and further,sufficient light resistance is also expressed. Therefore, the moldedarticle exhibits a good metallic feeling and a heavy luxury feeling evenif it is unpainted, so it is extremely useful in various fields such asautomobile exterior materials and industrial packaging materials forhousehold electric appliances.

MODES FOR CARRYING OUT THE INVENTION

[Polypropylene-Based Resin (A)]

The resin component in the polypropylene-based resin composition of thepresent invention is mainly a polypropylene-based resin (A). However,other resins (resins other than the polypropylene-based resin (A)) maybe contained together with the polypropylene-based resin (A). Theproportion of the polypropylene-based resin (A) in 100% by mass of theresin component is preferably 50 to 100% by mass, more preferably 70 to100% by mass. The type of the other resin is not particularly limited,and for example, polyethylene-based resins, polybutene-based resins,cyclic polyolefin-based resins, polyester resins, polyimide-basedresins, polystyrene-based resins, ABS resins, AES resins, AS resins,acrylic resins and polycarbonate-based resins can be used. As the otherresins, polyethylene-based resins are particularly preferred.

The polypropylene-based resin (A) includes, for example, at least one ormore propylene homopolymers, random copolymers composed of propylene andethylene and/or at least one or more monomers selected from olefinshaving 4 to 8 carbon atoms, and propylene block copolymers constitutedof 60 to 95% by mass of 23° C. n-decane-insoluble portion (Dinsol) and 5to 40% by mass of 23° C. n-decane-soluble portion (Dsol) (the total ofDinsol and Dsol is taken as 100% by mass).

The polyethylene-based resin as the other resin includes, for example,at least one or more ethylene homopolymers, ethylene copolymers havingan intrinsic viscosity [n] of 0.5 to 3.0 dl/g and a density of 850 to970 kg/m³ obtained by copolymerizing ethylene and one or more α-olefinsselected from α-olefins having 3 to 10 carbon atoms, high-pressureradical method low-density polyethylenes and ethylene-ethyl acetatecopolymers. The intrinsic viscosity [n] of the ethylene copolymer ispreferably 0.6 to 3.0, more preferably 0.6 to 2.5. The density of theethylene copolymer is preferably 850 to 920 kg/m³, more preferably 850to 900 kg/m³.

The polypropylene-based resin composition of the present invention maycontain an inorganic filler together with the polypropylene-based resin(A). The proportion of the polypropylene-based resin is preferably 70 to100 parts by mass, more preferably 80 to 100 parts by mass (providedthat, when the polypropylene-based resin contains other resins, theproportion of the total amount of the polypropylene-based resin and theother resins is preferably 70 to 100 parts by mass, more preferably 80to 100 parts by mass), and the proportion of the inorganic filler ispreferably 0 to 30 parts by mass, more preferably 0 to 20 parts by mass.These proportions are based on the case where the total amount of thepolypropylene-based resin, the other resins and the inorganic filler is100 parts by mass. The type of the inorganic filler is not particularlylimited and known inorganic materials can be used. Specific examplesthereof include talc, mica, calcium carbonate, barium sulfate, glassfiber, gypsum, magnesium carbonate, magnesium oxide and titanium oxide.Among them, talc is particularly preferable.

The polypropylene-based resin (A) can also be used by further mixingvarious additives such as a crystallization nucleating agent, alubricant, an antiblocking agent, a weathering stabilizer, aheat-resistant stabilizer and an antioxidant.

[Aluminum Flake (B)]

The aluminum flake (B) used in the present invention can be produced bya known method. Specifically, for example, it can be manufactured bypulverizing or grinding materials such as an atomized powder, analuminum foil or a vapor-deposited aluminum foil by a device such as aball mill, an attritor or a stamp mill. Particularly, preferred is analuminum flake obtained by grinding by a ball mill an aluminum powderobtained by an atomizing method. The purity of aluminum is notparticularly limited, and it may be an alloy with another metal as longas it has spreadability. Specific examples of the another metal includeSi, Fe, Cu, Mn, Mg and Zn.

The average particle size of the aluminum flake (B) is preferably 5 to90 μm, and more preferably 10 to 70 μm. One type of the aluminum flake(B) may be used alone, or two or more types thereof may be used incombination.

The amount of the aluminum flake (B) blended is 0.8 to 5.0 parts bymass, preferably 1.0 to 3.0 parts by mass with respect to 100 parts bymass of the polypropylene-based resin (A) (provided that, when thepolypropylene-based resin contains other resins and/or inorganic filler,the total amount of the polypropylene-based resin and other resinsand/or inorganic filler is taken as 100 parts by mass). If the blendingamount of the aluminum flake is too small, it is impossible to improve afeeling of luminance and a flip-flop metallic feeling. In contrast, ifthe blending amount of the aluminum flake is too large, mechanicalproperties such as impact strength may be deteriorated in some cases.

[Carbon Black (C)]

As the carbon black (C) used in the present invention, known carbonblacks can be used without particular limitation. The average particlesize of the carbon black (C) is also not limited, but its primaryparticle size is preferably 10 to 40 nm.

When only the aluminum flake is blended, a flicker-flop metallic feelingis weak, deriving from the fact that the difference in lightnessobtained by observation from the horizontal and diagonal directions(shade) and observation from the regular reflection direction(highlight) is not large. On the other hand, in the present invention,by addition of appropriate amounts of an aluminum flake (B) and carbonblack (C), the lightness of the aluminum flake (B) is not disturbed inobservation from the highlight, and the lightness of carbon black (C) isexerted in observation from the shade, and additionally, a sufficientfeeling of luminance is also obtained, surprisingly. Although itsmechanism is not necessarily clear, it is guessed that by addition of anappropriate amount of carbon black, it becomes possible to lower thelightness in shade direction by carbon black and to darken while keepingthe lightness in highlight direction by the aluminum flake bright, anddeep contrast is manifested and a flip-flop metallic feeling becomesmore pronounced, and a heavy luxury feeling and a feeling of luminanceare expressed.

Furthermore, by adding an appropriate amount of the carbon black (C),light resistance is more improved than the case of using only thealuminum flake (B) as the brightener.

The blending amount of the carbon black (C) is 0.005 to 0.06 parts bymass, preferably 0.008 to 0.03 parts by mass, more preferably 0.01 to0.02 parts by mass with respect to 100 parts by mass of thepolypropylene-based resin (A) (provided that, when thepolypropylene-based resin contains other resins and/or inorganic filler,the total amount of the polypropylene-based resin and other resinsand/or inorganic filler is taken as 100 parts by mass). When the amountof the carbon black (C) blended is too large, the lightness of the wholeis lowered by hiding power of the carbon black (C) and there is apossibility that the expression itself of the flip-flop metallic feelingis inhibited.

[Pigment (D)]

The polypropylene-based resin composition of the present invention maycontain a chromatic inorganic pigment and/or organic pigment (D) otherthan the carbon black (B). As the pigment (D), a known pigment can beused. Specific examples of the inorganic pigment include oxides,sulfides and sulfates of metals. Specific examples of the organicpigment include phthalocyanine type pigments, quinacridone type pigmentsand benzidine type pigments.

The blending amount of the chromatic inorganic pigment and/or organicpigment (D) (excluding carbon black) is preferably 0.01 to 0.70 parts bymass, more preferably 0.05 to 0.70 parts by mass, particularlypreferably 0.10 to 0.60 parts by mass with respect to 100 parts by massof the polypropylene-based resin composition (A) (provided that, whenthe polypropylene-based resin contains other resins and/or inorganicfiller, the total amount of the polypropylene-based resin, other resinsand/or inorganic filler is taken as 100 parts by mass).

[Various Additives]

To the polypropylene-based resin composition of the present invention,various additives such as a heat-resistant stabilizer, an antistaticagent, a weathering stabilizer, a light-resistant stabilizer, anantioxidant, a fatty acid metal salt and a dispersant can be blended ifnecessary, so long as the object of the invention is not impaired.

[Method for Producing Composition]

The polypropylene-based resin composition of the present invention canbe produced by mixing the above-mentioned components and, if necessary,various additives by a known method. For example, the components may bemixed by a mixer or tumbler, or the mixture may be melt-kneaded by anextruder. Furthermore, it may be processed into pellets in order toimprove the operability of the molding.

[Lightness]

When incident light is irradiated from the direction of 45° to thesurface of a test piece obtained by molding the polypropylene-basedresin composition of the present invention by the following injectionmolding method, the lightness in the highlight direction (L15°) and thelightness in the shade direction (L110°) defined below preferablysatisfy the following relationship.L15°/L110°≥3.3L110°≤27.0(Lightness in Highlight Direction (L15°))

When the regular reflection position of 90° with respect to the incidentlight at 45° is defined as 0°, the lightness in the highlight direction(L15°) is the lightness of the reflected light at an angle shiftedtoward the incident light direction side by 15° from this 0°.

(Lightness in Shade Direction (L110°))

When the regular reflection position of 90° with respect to the incidentlight at 45° is defined as 0°, the lightness in the shade direction(L110°) is the lightness of the reflected light at an angle shiftedtoward the incident light direction side by 110° from this 0°.

(Injection Molding Method)

The polypropylene-based resin composition is injection-molded underconditions in which the barrel temperature is higher by (20 to 120°) C.than the highest temperature of the glass transition temperature and/orcrystal melting temperature of the resin, the injection speed is 30 to50 mm/sec, the mold set temperature is lower by (50 to 100°) C. than thehighest temperature of the glass transition temperature and/orcrystallization temperature of the resin, the cooling time is 10 to 20seconds, and the mold clamping pressure is 30 to 80 t, to obtain a testpiece composed of a square plate with a thickness of 2 mm.

[Molded Article]

The polypropylene-based resin composition of the present invention canbe processed into various molded articles by a known processing method(for example, injection molding or extrusion molding). Among them, it issuitable for injection molding. The resulting molded article exhibits ahigh flip-flop metallic feeling, a heavy luxury feeling and a feeling ofluminance, so it can be used as a product without conducting post stepssuch as a coating step and a step of providing a skin.

The molded article of the present invention can be suitably used, forexample, as an automobile part or an industrial packaging material ofhousehold appliances. In particular, the molded article of the presentinvention is excellent in a flip-flop metallic appearance, a heavyluxury feeling, light resistance and a feeling of luminance, so it isparticularly useful as an automotive exterior material. The performanceand the level required for the outer package vary actually depending onvarious conditions such as the vehicle type and the exterior position.The molded article of the present invention is extremely useful as anexterior material requiring a particularly high level of luxury feelingand a feeling of luminance, for example, an exterior material of aluxury car or an exterior material of a place that always stands out(for example, a bumper garnish of a SUV car).

EXAMPLES

Hereinafter, the present invention will be described in more detailbased on examples, however, the present invention is not limited tothese examples. Details of each component are described below.

<Polypropylene-Based Resin (A)>

“P-1”: Block polypropylene (“Prime Polypro (registered trademark)J830HV” manufactured by Prime Polymer Co., Ltd., MFR (230° C., 2.16kg)=30 g/10 min)

<Other Resins>

“P-2”: ethylene-1-butene copolymer (“TAFMER (registered trademark)A0550” manufactured by Mitsui Chemicals, Inc., MFR=0.9 g/10 min,density=861 kg/m³)

<Inorganic Filler>

“Talc”: Talc (trade name “JM209”, manufactured by Asada Milling Co.,Ltd., average particle size=3.9 μm)

<Aluminum Flake (B)>

“Aluminum 1”: Aluminum master batch (manufactured by Toyo Aluminum K.K.,average particle size=20 μm, aluminum concentration=70%)

“Aluminum 2”: Aluminum master batch (manufactured by Toyo Aluminum K.K.,average particle size=60 μm, aluminum concentration=70%)

“Aluminum 3”: Aluminum master batch (manufactured by Toyo Aluminum K.K.,average particle size=10 μm, aluminum concentration=70%)

“Aluminum 4”: Aluminum master batch (manufactured by Toyo Aluminum K.K.,average particle size=70 μm, aluminum concentration=70%)

<Carbon Black (C)>

Trade name “BLACK PERLS 4840” manufactured by CABOT, average primaryparticle size=18 nm

<Pigment (D)>

Trade name “Ultramarine Blue NO. 57” manufactured by HOLLIDAY PIGMENTSLtd.

<Preparation of Resin Compositions (A-1) to (A-3)>

P-1, P-2 and talc were blended in the proportions shown in Table 1, toobtain resin compositions (A-1) to (A-3).

TABLE 1 P-1 P-2 Talc (A-1) 65 25 10 (A-2) 100 0 0 (A-3) 76 4 20

The maximum crystal melting temperature of the resin components of theresin compositions (A-1) to (A-3) was 162° C., the maximumcrystallization temperature thereof was 115° C., and the glasstransition temperature thereof was 0° C. or less. Based on thesetemperatures, the cylinder temperature of the injection molding machinewas determined to 190° C. (162° C.+28° C.) and the mold set temperaturewas determined to 45° C. (115° C.-70° C.). The crystal meltingtemperature and the crystallization temperature were measured by thefollowing method using DSC, and the glass transition temperature wasmeasured by the following method using a solid viscoelasticity measuringdevice.

(Crystal Melting Temperature and Crystallization Temperature)

The crystal melting temperature and the crystallization temperature weremeasured using a DSC 8500 apparatus manufactured by Perkin Elmer.Regarding the temperature at the maximum peak position in theendothermic curve and the exothermic curve, about 5 mg of a sample cutout from a press sheet having a thickness of about 300 μm was packed inan aluminum pan having the flat bottom and kept at 230° C. in a nitrogenatmosphere (nitrogen: 20 ml/min) for 5 minutes, then, the temperaturewas lowered from 230° C. down to 30° C. at 10° C./min, and thetemperature at the maximum peak in the exothermic curve of this processwas taken as the crystallization temperature. Further, it was kept at30° C. for 1 minute, then, the temperature was raised from 30° C. to230° C. at 10° C./min, and the temperature at the maximum peak in theendothermic curve of this process was taken as the crystal meltingtemperature.

(Glass Transition Temperature)

The pellets were press-molded to prepare a molded article, andtemperature dispersion measurement was carried out under the followingconditions using a solid viscoelasticity measuring device, and thehighest peak temperature at which tan 6, the ratio of the storageelastic modulus (E′) to the loss elastic modulus (E″), is maximum wastaken as the glass transition temperature.

Measuring device: RSA-II (manufactured by TA)

Measurement mode: Tension mode (Autotension, Autostrain control)

Measurement temperature: −80 to 150° C. (up to measurable temperature)

Heating rate: 3° C./min

Sample size: width 5 mm×thickness 0.4 mm

Initial Gap (L0): 21.5 mm

Atmosphere: N₂

Reference Example 1, Examples 1 to 12, Comparative Examples 1 to 10

The components were respectively blended in proportions shown in Table 2(addition amount of aluminum flake in the table is the amount ofaluminum flake in the masterbatch), and further, 0.10 parts by mass of ahindered phenol-based antioxidant (manufactured by Ciba SpecialtyChemicals Inc., trade name “IRGANOX1010FP”), 0.05 parts by mass of aphosphorus-based antioxidant (manufactured by Ciba Specialty ChemicalsInc., trade name “IRGA FOS168”) and 0.05 parts by mass of calciumstearate (manufactured by Nitto Chemical Industry Co., Ltd., trade name“Calcium Stearate”) were blended with respect to 100 parts by mass ofthe blend, and preliminarily mixed with a Henschel mixer. Next, meltkneading was carried out using a twin-screw extruder at a resintemperature of 210° C., the molten strand was cooled in a water tank,and polypropylene-based resin pellets were obtained with a strandcutter.

Using the above pellets, the following test pieces for each evaluationwere molded and evaluated, in Examples 1 to 12 and Comparative Examples1 to 10. In Reference Example 1, the following test pieces for eachevaluation were molded and a metallic synthetic resin enamel paint(trade name “NH-700 M (YK)” manufactured by Nippon Paint AutomotiveCoatings Co., Ltd.) was applied to the surface of the test piece, andthen, it was evaluated. Details of the evaluation method are as follows.Each evaluation result is shown in Table 2.

(1) Lightness (L)

A square plate of 50 mm×90 mm×2 mm thick was injection-molded under thefollowing conditions, and this was used as a test piece for lightnessmeasurement.

EC-40N II manufactured by Toshiba Machine Co., Ltd.

Cylinder temperature: 190° C.

Screw rotation speed: 110 rpm

Weighing time: 7.5 sec

Holding pressure: 40 MPa

Back pressure: 5 MPa

Injection speed: 40 mm/s

Mold clamping pressure: 40 t

Mold set temperature: 45° C.

Cooling time: 10 sec

As a lightness measuring device, a multi-angle spectrocolorimeter MA-98manufactured by X-rite Co., Ltd. was used and an L value which is alightness index of the obtained CIE colorimetric system was used. Then,incident light was irradiated from the direction of 45°, and thelightness in the highlight direction (L15°), that is, the lightness ofthe reflected light at the angle shifted by 15° from the regularreflection position 0° toward the incident light direction side(highlight direction) was measured, and the lightness in the shadedirection (L110°), that is, the lightness of the reflected light at theangle shifted by 110° from the regular reflection position 0° toward theincident light direction side (shade direction) was measured, and theratio) (L15°/L110° of both was calculated.

(2) Flip-Flop Type Metallic Feeling

As a test piece for evaluating a flip-flop metallic feeling, the samesquare plate of 50 mm×90 mm×2 mm thick as the test piece for measuringlightness described above was used. The lightness viewed perpendicularlyto the surface of this test piece and the lightness viewed horizontallywere visually confirmed and a flip-flop metallic feeling was evaluatedaccording to the following criteria.

A: Difference between the lightness viewed perpendicularly to thesurface of a test piece and the lightness viewed horizontally is verylarge.

B: Difference between the lightness viewed perpendicularly to thesurface of a test piece and the lightness viewed horizontally is large.

(3) Heavy Luxury Feeling

As a test piece for evaluating a heavy luxury feeling, the same squareplate of 50 mm×90 mm×2 mm thick as the test piece for measuringlightness described above was used. The surface of this test piece wasvisually confirmed, and a feeling of luminance was evaluated accordingto the following criteria.

A: When viewed horizontally with respect to the surface of a test piece,it looks deep black.

B: When viewed horizontally with respect to the surface of a test piece,it looks slightly deep black.

C: When viewed horizontally with respect to the surface of a test piece,it looks slightly blackish.

(4) Light Resistance

As a test piece for evaluating light resistance, the same square plateof 50 mm×90 mm×2 mm thick as the test piece for measuring lightnessdescribed above was used. As an evaluation equipment, a xenon weathermeter was used, and an exposure test was carried out for 100 to 500hours under conditions of a black panel temperature of 83° C. and anirradiation energy of 60 W/m², the change of the sample surface wasvisually confirmed, and light resistance was evaluated according to thefollowing criteria.

A: No discoloration or cracking on the surface.

B: Almost no discoloration or cracking on the surface.

C: Discoloration and cracking are observed on the surface.

D: Discoloration and cracking on the surface are intense.

TABLE 2 Carbon Aluminum Flake (B) Black (C) Pigment (D) Resin AdditionAddition Addition Composition Amount Amount Amount Lightness Flip-flopHeavy parts by (parts by (parts by (parts by L15°/ Metallic Luxury LightType mass Type mass) mass) mass) L110° L110° Feeling Ffeeling ResistanceRef. Ex. 1 A-1 100 Painting of Metallic Synthetic Resin 5.63 27.52 A B —Enamel Paint Containing the Brightener Ex. 1 A-1 100 Aluminum 1 1 0.01 —4.47 23.06 A A B Ex. 2 A-1 100 Aluminum 1 1 0.05 — 6.47 13.34 A A AComp. Ex. 1 A-1 100 Aluminum 1 1 0 — 3.06 35.41 B C C Ex. 3 A-1 100Aluminum 1 2 0.01 — 4.91 23.47 A A B Ex. 4 A-1 100 Aluminum 1 5 0.01 —4.78 26.01 A A B Comp. Ex. 2 A-1 100 Aluminum 1 2 0 — 3.78 31.27 B C CComp. Ex. 3 A-1 100 Aluminum 1 5 0 — 4.38 28.89 B C D Ex. 5 A-1 100Aluminum 2 1 0.01 — 3.47 25.05 A A B Comp. Ex. 4 A-1 100 Aluminum 2 1 0— 2.41 39.96 B C D Ex. 6 A-2 100 Aluminum 1 1 0.01 — 4.87 25.02 A A BEx. 7 A-2 100 Aluminum 2 1 0.01 — 4.41 22.78 A A B Comp. Ex. 5 A-2 100Aluminum 1 1 0 — 4.38 27.94 B B C Comp. Ex. 6 A-2 100 Aluminum 2 1 0 —3.36 32.58 B C D Ex. 8 A-3 100 Aluminum 1 1 0.01 — 4.59 23.75 A A B Ex.9 A-3 100 Aluminum 2 1 0.01 — 3.39 26.90 A A B Comp. Ex. 7 A-3 100Aluminum 1 1 0 — 3.35 34.52 B C C Comp. Ex. 8 A-3 100 Aluminum 2 1 0 —2.43 41.22 B C D Ex. 10 A-1 100 Aluminum 1 1 0.01 0.3 3.88 26.79 A A BEx. 11 A-2 100 Aluminum 3 1 0.01 — 4.82 24.52 A A B Ex. 12 A-2 100Aluminum 4 1 0.01 — 4.63 19.09 A A B Comp. Ex. 9 A-2 100 Aluminum 3 1 0— 4.17 29.10 B B C Comp. Ex. 10 A-2 100 Aluminum 4 1 0 — 2.93 34.76 B CD<Evaluation>

As is apparent from the results shown in Table 2, the molded articles ofExamples 1 to 12 to which an appropriate amount of carbon black wasadded were excellent in a flip-flop metallic feeling and a heavy luxuryfeeling, and also excellent in light resistance, as compared with themolded articles of Comparative Examples 1 to 10 without addition ofcarbon black.

Lowering of the lightness in the shade direction is a phenomenonoccurring by addition of an appropriate amount of carbon blackregardless of the average particle size/addition amount of an aluminumflake, the presence or absence of pigments other than carbon black, thekind of the resin and the addition amount of an inorganic filler, andthis phenomenon and the fact that the value obtained by dividing thelightness in highlight direction by the lightness in shade direction islarge are guessed to improve a flip-flop metallic feeling and a heavyluxury feeling.

Examples 13 to 14, Comparative Examples 11 to 12

Pellets were prepared in the same manner as in Examples 1 to 12 exceptthat the proportion of each component was changed to the proportionshown in Table 3. Using the pellets, test pieces for evaluating thelightness (L) described above and test pieces for evaluating a feelingof luminance described below were molded and evaluated. Details of theevaluation method of a feeling of luminance are as follows. Eachevaluation result is shown in Table 3.

(5) Feeling of Luminance

As a test piece for a feeling of luminance, a square plate of 50 mm×90mm×1 mm thick differing only in thickness from the test piece formeasuring lightness described above was used. The surface of this testpiece was visually confirmed, and a feeling of luminance was evaluatedaccording to the following criteria.

A: Very high gloss feeling like a polished metal surface.

B: High gloss feeling like a polished metal surface.

TABLE 3 Carbon Aluminum Flake (B) Black (C) Pigment (D) Resin AdditionAddition Addition Composition Amount Amount Amount Lightness parts by(parts by (parts by (parts by L15°/ Feeling of Type mass Type mass)mass) mass) L110° L110° Lluminance Ex. 13 A-2 100 Aluminum 1 0.9 0.01 —6.0 19.71 A Comp. Ex. 11 A-2 100 Aluminum 1 0.6 0.01 — 5.7 19.85 B Ex.14 A-2 100 Aluminum 2 0.9 0.01 — 4.4 22.33 A Comp. Ex. 12 A-2 100Aluminum 2 0.6 0.01 — 4.5 19.69 B<Evaluation>

The feeling of luminance could not be quantified, and the reflectance inExample 13 (610 nm) was 38.36% and the reflectance in ComparativeExample 11 (610 nm) was 35.94%, the reflectance of the molded articlebeing considered to be a factor of the feeling of luminance.

INDUSTRIAL APPLICABILITY

The polypropylene-based resin composition and the molded article of thepresent invention are excellent in a flip-flop metallic appearance, aheavy luxury feeling, light resistance and a feeling of luminance, sothey are useful in various fields such as automobile exterior materialsand industrial packaging materials for home electrical appliances.

The invention claimed is:
 1. A polypropylene-based resin composition,comprising a polypropylene-based resin (A) as the only resin componentof the composition, or the polypropylene-based resin (A) and apolyethylene-based resin as the only resin components of thecomposition, and which comprise: 100 parts by mass of apolypropylene-based resin (A) (provided that, when thepolypropylene-based resin composition contains the polyethylene-basedresin and/or inorganic fillers, the total amount of thepolypropylene-based resin (A) and the polyethylene-based resin and/orinorganic fillers is taken as 100 parts by mass), 0.80 to 5.0 parts bymass of one or more kinds of aluminum flakes (B) having an averageparticle size of 5 to 90 μm and 0.008 to 0.03 parts by mass of carbonblack (C) and, wherein, when incident light is irradiated from thedirection of 45° to the surface of a test piece obtained by molding thepolypropylene-based resin composition by the following injection moldingmethod, the lightness in the highlight direction)(L15°) and thelightness in the shade direction)(L110°) defined below satisfy thefollowing relationships:L15°/L110°≥3.3  1.L110°≤27.0  2.[Lightness in highlight direction (L15°)] 
 3. When the regularreflection position of 90° with respect to the incident light at 45° isdefined as 0°, the lightness in the highlight direction)(L15°) is thelightness of the reflected light at an angle shifted toward the incidentlight direction side by 15°) from this 0°,[Lightness in shade direction (L110°)] 
 4. When the regular reflectionposition of 90° with respect to the incident light at 45° is defined as0°, the lightness in the shade direction)(L110°) is the lightness of thereflected light at an angle shifted toward the incident light directionside by 110°) from this 0°,[Injection Molding Method] 
 5. The polypropylene-based resin compositionis injection-molded under conditions in which the barrel temperature ishigher by (20 to 120°) C. than the highest temperature of the glasstransition temperature and/or crystal melting temperature of thepolypropylene-based resin (A) and the polyethylene-based resin, theinjection speed is 30 to 50 mm/sec, the mold set temperature is lower by(50 to 100°) C. than the highest temperature of the glass transitiontemperature and/or crystallization temperature of thepolypropylene-based resin (A) and the polyethylene-based resin, thecooling time is 10 to 20 seconds, and the mold clamping pressure is 30to 80 t, to obtain a test piece composed of a square plate with athickness of 2 mm.
 2. The polypropylene-based resin compositionaccording to claim 1, further comprising 0.01 to 0.70 parts by mass of achromatic inorganic pigment and/or organic pigment (D) (excluding carbonblack).
 3. The polypropylene-based resin composition according to claim1, comprising 70 to 100 parts by mass of the polypropylene-based resin(A) as the only resin component of the composition and 0 to 30 parts bymass of an inorganic filler.
 4. A molded article obtained byinjection-molding the polypropylene-based resin composition according toclaim
 1. 5. The molded article according to claim 4, which is anautomotive exterior material.
 6. The polypropylene-based resincomposition according to claim 1, comprising 70 to 100 parts by mass ofthe polypropylene-based resin (A) and the polyethylene-based resin asthe only resin components of the composition and 0 to 30 parts by massof an inorganic filler.